JPH03213700A - Motor fan - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a structure for reducing noise of an electric blower in a vacuum cleaner.

[Conventional technology]

As described in Japanese Patent Laid-Open No. 62-237099, a conventional electric blower has an air guide and a load-side bracket of a motor integrally formed, and the outer periphery of the air guide is extended toward the anti-load side bracket. The outer periphery of the exhaust port of the load bracket is covered to form a soundproof cylinder, and the soundproof cylinder is filled with sound-absorbing material. In other words, the noise generated as the fan rotates enters the motor through the air guide, passes between the rotor and stator, exits from the exhaust port on the anti-load side bracket, and passes through the sound-absorbing material inside the soundproof tube. In addition to absorbing sound, the positions of the exhaust port on the anti-load side bracket and the exhaust port formed on the outer cylindrical part of the air guide are misaligned, so that direct sound does not come out from the exhaust port. The wall that used to be just a bracket became a double wall with the outer cylindrical part of the air guide, making it possible to reduce noise.

[Problem to be solved by the invention]

The above-mentioned conventional technology absorbs sound using a breathable sound-absorbing material, but generally the sound-absorbing coefficient of the sound-absorbing material is high in the high frequency band of 2 KHz or more, and when the thickness is about 20 mm, the sound absorption coefficient is low in the low frequency band of 2 KHz or less. .

On the other hand, since the frequency that poses a problem with the noise of the vacuum cleaner as a whole is mainly in the low frequency band below 2KHz, in order to achieve lower noise, it is necessary to increase the thickness or length of the sound-absorbing material. There was a problem in that the electric blower became larger or more expensive.

After cooling the rotor and stator, the airflow that enters the motor passes through the sound-absorbing material in the sound-proof cylinder, so the sound-absorbing material becomes a resistor and increases ventilation loss. There was a problem that the

In addition, there is a risk that sparks generated between the brush and the condominium may fly out, pass through the exhaust port, adhere to the sound absorbing material, and cause it to flex.

Since the exhaust port on the anti-load side bracket and the exhaust port on the outer cylindrical part of the air guide are set to be offset from each other, the airflow coming out of the former exhaust port goes around, joins near the latter exhaust port, and is discharged. At this time, there was a problem in that the airflows collided when they merged, resulting in airflow noise and increased noise.

An object of the present invention is to reduce noise in a low frequency band without increasing the size of an electric blower or reducing aerodynamic performance, and to provide a vacuum cleaner with low noise. be.

[Means to solve the problem]

In order to achieve the above object, a frame body communicating with an exhaust port is provided on the outer periphery of the housing, and an exhaust passage formed by the frame body and the housing has a uniform cross-sectional area.

Furthermore, in order to further reduce the size of the electric blower, an exhaust passage formed by the frame and the housing and having a uniform cross-sectional area is provided in the axial direction.

Furthermore, in order to reduce noise in high frequency bands, a sound absorber is housed on the back side of the end bracket of the motor.

In addition, in order to further reduce noise in the low frequency band, an exhaust passage having a uniform area formed by the frame and the housing is provided in the circumferential direction, and the length of the passage is increased.

[Effect]

Noise generated from the impeller enters the motor and exits from the exhaust port on the outer periphery of the housing, but if the flow path after the impeller is considered as a type of acoustic filter, the low frequency range becomes a lumped constant range and has acoustic characteristics. is the resonance frequency io under peak (the value at this time is usually smaller than 1).
The spectrum is as follows. Here, the volume of the flow path to the exhaust port is V, the cross-sectional area of the exhaust passage is S, and its length is Q.
Then, the resonant frequency fo can be found by the following equation.

If the position of this resonant frequency io can be shifted to a low frequency range, the noise in the low frequency range can be reduced, and this can be achieved by increasing the length Q of the exhaust passage.

According to this configuration, since the exhaust passage length Q having a uniform cross-sectional area with the exhaust port is ensured, the low frequency range can be reduced.

Further, by providing the exhaust passage in the axial direction, it is possible to promote miniaturization of the electric blower.

Furthermore, since the sound absorbing body is housed in the front face of the exhaust side, it is possible to reduce excessive noise, thereby achieving further noise reduction.

By providing the exhaust passage in the circumferential direction, a long passage length can be ensured, and the resonant frequency fO can be further shifted to a lower frequency range.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The electric blower consists of a blower 1 and an electric motor 2. Electric motor 1
The housing 3 has a bearing holding part 3a for holding the bearing 5 of the rotor 4 in the center, an exhaust port 3b for discharging airflow that cools the inside of the motor, and ribs 3c on the outer periphery. A frame body 6 configured with an area is press-fitted and fixed to the front rib 3c,
It forms an exhaust passage 6a and is fixed to the end bracket 7 with screws. The end bracket 7 is composed of a bearing holding part 7a, an annular flat part 7b on the outer periphery, and a supporting arm part connecting these parts. 8 is formed.

A diffuser 9 is arranged on the end bracket 7,
Upstream thereof, a centrifugal impeller 1o is integrally fixed to the rotating shaft 11 of the rotor 4 with a nut 12.

A fan casing 13 covers the centrifugal impeller 10 and the diffuser 9 and is press-fitted onto the outer periphery of the end bracket 7. Here, the diffuser 9 includes a plurality of diffuser blades 14 on the outer peripheral extension of the centrifugal impeller 10.
and a return guide vane 15 on the rear side thereof, and the return guide vane 15 forms, together with the end bracket 7, a return passage that guides the exhaust flow to the intake port 8.

The operation of the above configuration will be explained. The centrifugal impeller 10 rotates as the rotor 4 is driven. This rotation causes
The airflow sucked in from the suction port 16 is discharged by the impeller 10, passes between the diffuser blades 14, changes the direction of the flow path at the outer periphery, passes through the return passage 15, enters the inside of the electric motor 2, and enters the rotor. 4 and the stator 17, and is directed toward the exhaust port 3b on the outer periphery of the housing 3, passes through the exhaust passage 6a formed by the frame 6, and is discharged to the outside air. In this way, the noise generated by the centrifugal impeller 10 is transmitted to the diffuser 9,
Alternatively, while being repeatedly compressed and expanded in the return passage 15 and further within the electric motor 3, it exits the exhaust port 3b of the housing 3, passes through the frame body 6a configured with a uniform cross-sectional area, and exits to the outside air. At this time, as shown in Figure 2, the flow path after the impeller is regarded as a muffler, the volume of the motor is V, the passage length of the frame is Q, the cross-sectional area of the exhaust passage is S, and the acoustic system Considering, as shown in (b), the resonant frequency f.

Acoustic characteristics having an underpeak are obtained, and the following formula % Formula % As a result, the resonance frequency fo can be shifted to a lower frequency because the exhaust passage Q having a constant cross-sectional area is secured.

FIG. 3 is a diagram showing the results of a 173-octave analysis of the noise of an electric blower. Result B is for a conventional electric blower without a frame, and result A is for an embodiment of the present invention. .

In this result, the noise was reduced by 7 to 15 dB in the low frequency band from 400 Hz to IKHz, and it is considered that the addition of the wooden frame 6 caused the resonant frequency fo to shift to a lower frequency. Furthermore, the noise decreased even in the high frequency band of 2 KHz or higher, which is thought to be due to a change in the acoustic characteristics of the electric blower as a whole, and as a result of this example, it was possible to reduce the noise by an overall value of ~dB.

4 to 6 show another embodiment 1, and FIG. 4 shows a uniform structure formed by the frame 18 and the outer wall of the housing 3, communicating with the exhaust port 3b on the outer periphery of the housing 3. An exhaust passage 18a having a cross-sectional area is provided in the axial direction. According to this, sound is directly emitted to the outside air from the exhaust port 3b of the housing 3, and is emitted after being refracted, and the exhaust passage length Q can be maintained, further reducing noise in the low frequency band. is obtained. This embodiment can be made smaller than the outermost diameter of the casing 13, and is excellent in terms of miniaturization. In FIG. 5, in addition to this embodiment, a sound absorber 19 is housed on the back side of the end brat 7. Therefore, the low frequency band is reduced and the eddy sound is absorbed by the sound absorber 19 when the exhaust flow passes through the sound absorber 19, thereby further reducing noise.

In FIG. 6, an exhaust passage 18a is provided in the circumferential direction. Since the length Q of the exhaust passage 18a can be ensured to be the longest, the resonance frequency fo can be shifted to a lower frequency range, and further noise reduction can be achieved.

〔Effect of the invention〕

According to the present invention, noise can be reduced in a low frequency range where noise reduction is difficult. In this example, the frequency is 7 to 15 below I KHz.
Can be reduced by dB.

[Brief explanation of drawings]

FIG. 1(a) is a partial cross-sectional view of the entire electric blower according to an embodiment of the present invention, FIG. 1(b) is a plan view of the electric motor, FIG. 1(c) is a perspective view of the electric blower, and FIG. is an explanatory diagram of a silencer, (
b) is an acoustic characteristic diagram of the silencer, FIG. 3 is an explanatory diagram showing the results of noise frequency analysis, and FIGS. 4, 5, and 6 are diagrams showing other embodiments. (a) is a partial sectional view of the entire electric blower, (b) is a plan view thereof, (C) is a perspective view thereof, and FIG. 7 is a partial sectional view of the entire conventional electric blower. 3...Housing, 3b...Exhaust port, 6...Frame, 6a'#, I L, 1 (b) (su8 ￥ figure

Claims (1)

[Claims] 1. An electric motor consisting of a housing having an exhaust port, an end bracket having an intake port, a rotor and a stator contained therein, a centrifugal impeller connected to the rotating shaft of the electric motor, and the impeller. An electric blower comprising a flat plate on the back surface of the housing, a diffuser having return guide vanes on the rear surface of the flat plate, and a fan casing on the outside of the diffuser, the frame communicating with the exhaust port on the outer periphery of the housing. An electric blower characterized in that an exhaust passage formed by the frame body and the housing has a uniform cross-sectional area.